Unicondylar knee implants and insertion methods therefor

ABSTRACT

A method of preparing a knee joint for receiving a unicondylar knee implant includes preparing a first seating surface at a proximal end of a tibia, and providing a combination bur template and spacer block, the bur template having an upper end, a lower end and a curved surface extending between the upper and lower ends thereof that is adapted to conform to a femoral condyle of a femur and the spacer block extending from the lower end of the bur template and having top and bottom surfaces. The method includes flexing the knee joint so that the prepared first seating surface at the proximal end of the tibia opposes a posterior region of the femoral condyle and inserting the combination bur template and spacer block into the knee joint so that the top surface of the spacer block engages the posterior region of the femoral condyle and the bottom surface of the spacer block engages the first seating surface at the proximal end of the tibia. While the spacer block is maintained between the femur and the tibia, the knee joint is extended until the curved surface of the bur template engages the femoral condyle of the femur. The bur template is anchored to the femur and used to guide burring of the femoral condyle for preparing a second seating surface on the femur. After burring the distal end of the femoral condyle, the posterior region of the femoral condyle is resected.

BACKGROUND OF THE INVENTION

The present invention generally relates to implants and morespecifically relates to method and apparatus for preparing bone forreceiving an implant.

The use of prosthetic implants to replace damaged natural joints, orportions of such joints, in the body has become widespread as medicaland technological advances have joined to provide improved materials andconfigurations for prosthetic implants and innovative procedures forimplanting these devices. The basic objective of such devices andprocedures is to provide a repaired joint of maximum effectiveness, witha minimal intrusion into the body. Component parts of these prostheticimplants are utilized to replace portions of a natural joint which havebecome damaged, either through injury or disease, and it is usuallynecessary to remove portions of the natural joint beyond merely thedamaged portions in order to enable stable and secure fixation of thecomponent parts to the natural bone. In addition, access to damagedjoints is limited and the necessity for reaching the areas to be workedupon can affect the extent of intrusion required to complete aneffective implant.

Improved methods for implanting a prosthetic device are disclosed incommonly assigned U.S. Pat. No. 6,554,838, the disclosure of which ishereby incorporated by reference herein. In certain preferredembodiments of the '838 patent, a method for preparing a seating surfacefor an implant includes positioning a guide on bone, the guide having aguide slot following a path geometrically similar to the peripheralboundary of the seating surface, inserting a cutting device through theguide slot at any selected location along the path of the guide slot,and translating the cutting device along the guide slot to cut anoutline groove in the bone coincident with the peripheral boundary ofthe seating surface. The guide is removed from the bone, and portions ofthe bone lying within the area delineated by the outline groove areremoved to establish the seating surface. The methods disclosed in the'838 patent provide numerous advantages including minimizing the amountof natural bone that must be removed and attaining accuracy in thedelineation of the area, depth and contour configuration of the preparedsurfaces of the bone that will receive the implant

In spite of the above advances, there remains a need for improvedmethods and apparatus for preparing bone for receiving implants andimplanting the prosthetic devices.

SUMMARY OF THE INVENTION

In certain preferred embodiments of the present invention, a method ofpreparing a knee joint for receiving a unicondylar knee implant includespreparing a first seating surface at a proximal end of a tibia such asby resecting the proximal end of the tibia. The method desirablyincludes providing a combination bur template and spacer block. The burtemplate and spacer block are preferably integrally connected together.In certain preferred embodiments, the bur template and the spacer blockare permanently connected together. The bur template and the spacerblock desirably form a single, rigid element. The bur templatepreferably has an upper end, a lower end and a curved surface extendingbetween the upper and lower ends thereof that is adapted to conform to afemoral condyle of a femur and the spacer block extends from the lowerend of the bur template and has top and bottom surfaces.

The method desirably includes flexing the knee joint so that theprepared first seating surface at the proximal end of the tibia opposesa posterior region of the femur. The combination bur template and spacerblock may be inserted into the knee joint so that the top surface of thespacer block engages the posterior region of the femur and the bottomsurface of the spacer block engages the first seating surface at theproximal end of the tibia. While the spacer block is maintained betweenthe femur and the tibia, the knee joint is extended until the curvedsurface of the bur template engages the femoral condyle of the femur.The bur template may be anchored to the femur, such as by using pins.The bur template is preferably used for guiding burring of the femoralcondyle for preparing a second seating surface on the femur. Afterburring the femoral condyle of the femur, the posterior region of thefemur is desirably resected.

The method may also include determining a distance between the firstseating surface on the tibia and the posterior region of the femur, andselecting one of a plurality of combination bur template and spacerblocks for inserting into the knee joint. The spacer block of theselected bur template preferably has a thickness that matches thedetermined distance between the first seating surface on the tibia andthe posterior region of said femur. In certain preferred embodiments,the thickness of the spacer block preferably corresponds to thethickness of a prostehtic device placed in the gap between the firstseating surface on the tibia and the posterior region of the femur. Thecombination bur template and spacer block desirably includes analignment feature. In certain preferred embodiments, the alignmentfeature is formed at a trailing end of the spacer block.

The method may also include inserting an alignment rail of a posteriorresection guide locator into the alignment feature formed in thetrailing end of the spacer block. The posterior resection guide locatordesirably includes at least one pin opening that overlies the alignmentrail. When the alignment rail is inserted into the alignment featureformed in the spacer block, the at least one pin opening of theposterior resection guide locator is preferably aligned with an openingof the bur template. A pin may be inserted through the at least one pinopening, through the opening in the bur template and anchored in thefemur. In other preferred embodiments, two or more pins are insertedthrough two or more respective pin openings in the posterior resectionguide locator.

The method may also include disengaging the posterior resection guidelocator from engagement with the combination bur template and spacerguide and sliding a posterior resection guide over said at least one pinin said femur.

In other preferred embodiments of the present invention, a method ofpreparing seating surfaces in a knee joint for receiving a unicondylarknee implant includes preparing a first seating surface for receiving atibial component at a proximal end of a tibia, flexing the knee joint sothat the first seating surface opposes a posterior region of the femoralcondyle, and providing a combination bur template and spacer block. Thebur template preferably has a curved surface extending between upper andlower ends thereof and the spacer block desirably extends from the lowerend of the bur template. The spacer block is preferably inserted intothe knee joint so that the spacer block engages the posterior region ofthe femoral condyle and the first seating surface on the tibia. Whilethe spacer block is maintained between the femur and the tibia, the kneejoint is desirably extended until the curved surface of the bur templateengages a distal region of the femoral condyle.

The method may include using the bur template to guide burring of thedistal region of the femoral condyle for preparing a second seatingsurface for receiving a femoral component. After the second seatingsurface has been prepared, one or more alignment pins may be anchored inthe femoral bone at the second seating surface. The one or morealignment pins anchored in the femoral bone may be used for aligning aposterior resection guide with the posterior region of the femoralcondyle. The posterior resection guide preferably has a slot for guidinga cutting instrument. The posterior resection guide is desirably usedfor resecting the posterior section of the femur.

In other preferred embodiments of the present invention, a kit forpreparing a knee joint for receiving a unicondylar knee implant includesa combination bur template and spacer block having a bur template withan upper end, a lower end and a curved inner surface extending betweenthe upper and lower ends thereof, and a spacer block extending from thelower end of said the template. The spacer block may have a top surface,a bottom surface, a leading end for insertion into a knee joint and atrailing end spaced from the leading end and adjacent the lower end ofthe bur template. The trailing end of the spacer block preferablyincludes an opening with an alignment feature that extends from thetrailing end of the spacer block toward the leading end of the spacerblock.

The kit may also include a posterior resection guide locator having analignment rail insertible into the opening at the trailing end of thespacer block. The alignment rail is preferably adapted to mesh with thealignment feature in the opening of the spacer block. In certainpreferred embodiments, the alignment rail has an elongated projectionand the alignment feature in the spacer block has an elongated groovethat receives the elongated projection. In other preferred embodiments,the alignment rail may have an elongated groove and the alignmentfeature in the spacer block may have an elongated projection that fitsinto the groove.

The posterior resection guide locator preferably includes an alignmentpin guide overlying the alignment rail. The alignment pin guidedesirably includes at least one pin opening extending therethrough.

The bur template preferably includes a guide rail extending around anouter perimeter thereof and a central opening surrounded by the guiderail. The at least one pin opening of the alignment guide is preferablyaligned with the central opening when the alignment rail is insertedinto the opening of the spacer block. An alignment pin is insertibleinto the at least one pin opening of the alignment guide.

The kit may also include a posterior resection guide having an upperend, a lower end having an elongated opening for receiving a cuttingtool and a pin opening between the upper and lower ends. The pin openingof the posterior resection guide is desirably slidable over thealignment pin. The pin opening may include a first set of pin openingsand a second set of pin openings that is closer to the upper end of theposterior resection guide than the first set of pin openings. The pinopening may also include a third set of pin openings that is closer tothe lower end of the posterior resection guide than the first set of pinopenings. As will be described in more detail below, the different setsof pin openings may be used for adjusting the amount of bone resectedfrom the posterior region of the femoral condyle.

These and other preferred embodiments of the present invention will bedescribed in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1J show a method of preparing a knee to receive a unicondylarknee implant, in accordance with certain preferred embodiments of thepresent invention.

FIG. 2 shows a tibial resection block and a locking element securablethereto, in accordance with certain preferred embodiments of the presentinvention.

FIGS. 3A-3D show the tibial resection block of FIG. 2 secured to a rod,in accordance with certain preferred embodiments of the presentinvention.

FIG. 4 shows a saggital resection alignment guide, in accordance withcertain preferred embodiments of the present invention.

FIGS. 5A-5E show a modular handle, in accordance with certain preferredembodiments of the present invention.

FIGS. 6A-6H show a combination bur template and spacer block, inaccordance with certain preferred embodiments of the present invention.

FIGS. 7A-7D show a shim engageable with the combination bur template andspacer block shown in FIGS. 6A-6H, in accordance with certain preferredembodiments of the present invention.

FIGS. 8A-8E show an alignment tower, in accordance with preferredembodiments of the present invention.

FIGS. 9A-9E show a posterior resection guide locator, in accordance withcertain preferred embodiments of the present invention.

FIGS. 10A-10D show a posterior resection guide, in accordance withcertain preferred embodiments of the present invention.

FIGS. 11A-11C show a posterior resection guide, in accordance with otherpreferred embodiments of the present invention.

FIGS. 12A-12F show a femoral trial cutting guide, in accordance withcertain preferred embodiments of the present invention.

FIG. 13A shows a handle attachable to the femoral trial cutting guide ofFIGS. 12A-12F, in accordance with certain preferred embodiments of thepresent invention.

FIG. 13B shows a drill passable through an opening in the femoral trialcutting guide of FIGS. 12A-12F and the handle of FIG. 13A.

FIGS. 14A-14E show the handle of FIG. 13A.

FIGS. 15A-15D show a punch tower for forming keel openings in tibialbone, in accordance with certain preferred embodiments of the presentinvention.

FIGS. 16A-16C show the punch tower shown in FIGS. 15A-15D.

FIGS. 17A-17D show a chisel for use with the punch tower shown in FIGS.15A-15D.

FIGS. 18A-18D show a tamp for use with the punch tower shown in FIGS.15A-15D.

FIG. 19 shows a tibial template, in accordance with certain preferredembodiments in the present invention.

FIG. 20 shows a holder for tibial templates having different sizes, inaccordance with certain preferred embodiments of the present invention.

FIGS. 21A-21E show the tibial template of FIG. 19.

FIGS. 22A-22D show a spacer for evaluating flexion and extension gaps,in accordance with certain preferred embodiments of the presentinvention.

FIGS. 23-32 show a method of resecting a proximal end of a tibia, inaccordance with certain preferred embodiments of the present invention.

FIGS. 33-37 show a method of aligning the combination bur template andspacer block of FIGS. 6A-6H in a knee joint, in accordance with certainpreferred embodiments of the present invention.

FIG. 38 shows the bur template/spacer block of FIGS. 6A-6H securedbetween a tibia and a femur, in accordance with certain preferredembodiments of the present invention.

FIGS. 39-43 show a method of resecting a posterior region of a femoralcondyle, in accordance with certain preferred embodiments of the presentinvention.

FIGS. 44-56 show a method of forming a keel opening at the proximal endof a tibia, in accordance with certain preferred embodiments of thepresent invention.

FIGS. 57-59 show a method of making openings for a post and a fin of afemoral component, in accordance with certain preferred embodiments ofthe present invention.

FIGS. 60-62 show a prior art bur template.

FIGS. 63A-63B show the spacer of FIGS. 22A-22D positioned between anextended knee joint.

FIGS. 64A-64B show the spacer of FIGS. 22A-22D positioned between aflexed knee joint.

FIG. 65 shows a gap balancing table, in accordance with certainpreferred embodiments of the present invention.

FIG. 66 shows a saggittal view of a flexed knee joint with a combinationbur template and spacer block inserted into the knee joint.

FIG. 67 shows a posterior resection guide locator coupled with acombination bur template and spacer block, in accordance with certainpreferred embodiments of the present invention.

FIG. 68 shows the posterior resection guide shown in FIGS. 10A-10D.

FIG. 69 shows the posterior resection guide shown in FIGS. 11A-11C.

FIGS. 70A and 70B show a method of aligning a knee implant, inaccordance with certain preferred embodiments of the present invention.

FIG. 71 shows a perspective view of a bur template/spacer block and shimengageable therewith, in accordance with certain preferred embodimentsof the present invention.

FIG. 72 shows a perspective view of a bur template/spacer block and shimengageable therewith, in accordance with another preferred embodiment ofthe present invention.

FIGS. 73-76 show a method of inserting a femoral component of a kneeimplant, in accordance with another preferred embodiment of the presentinvention.

FIGS. 77A-77B show a femoral component of a knee implant, in accordancewith certain preferred embodiments of the present invention.

FIGS. 78A-78B show a tibial component of a knee implant, in accordancewith certain preferred embodiments of the present invention.

FIG. 79 shows the femoral component of FIGS. 77A-77B and the tibialcomponent of FIGS. 78A-78B implanted in a knee joint.

DETAILED DESCRIPTION

FIGS. 1A-1J show a method of preparing a knee for receiving an implant,in accordance with certain preferred embodiments of the presentinvention. In particular preferred embodiments, the method is used forpreparing a knee to receive a knee implant such as a unicondylar kneeimplant. Referring to FIG. 1A, a knee joint 100 is located between aproximal end 102 of a tibia 104 and a distal end 106 of a femur 108. Thedistal end 106 of the femur 108 includes a distal condyle 110, which isthe curved surface on a bone where it forms a joint with another bone.The femur 108 also has a posterior region of the femoral condyle.

In FIG. 1A, a tibial resection is performed on the proximal end 102 ofthe tibia 104. FIG. 1B shows a saggital resection being performed on theproximal end 102 of the tibia 104. FIG. 1C shows the positioning andalignment of a combination bur template and spacer block in a kneejoint. The combination bur template and spacer block includes a spacerblock that is inserted into the knee joint between the femur and thetibia and the bur template that guides burring of the condyle at thedistal end of the femur. The bur template and spacer block is alignedfemur 108 using an alignment flag, as will be described in more detailbelow. FIG. 1D shows the bur template/spacer blocks after it has beenpositioned in a knee joint. The bur template includes a rail thatsurrounds a central opening. The rail preferably guides movement of aburring instrument after the burring instrument is passed through thecentral opening of the bur template. FIG. 1E shows a posterior resectionguide locator assembled with the combination bur template and spacerguide and alignment pins extending through pin openings in the posteriorresection guide locator. FIG. 1F shows the alignment pins shown in FIG.1E being used to align a posterior resection guide for performing aposterior resection of the femur 108. FIG. 1G shows a femoral trialcutting guide used for forming post and fin openings on the condyle 110located at the distal end 106 of the femur 108. FIGS. 1H-1J show amethod of forming a keel opening at the proximal end 102 of the tibia104.

Referring to FIG. 2, in certain preferred embodiments of the presentinvention, a system for preparing a knee joint for receiving aunicondylar knee implant includes a tibial resection block 112 having atop surface 114, an inner contoured surface 116 that is preferablyshaped to fit against the proximal end of a tibia and an outer contouredsurface 118 that is adapted to fit easily within an incision. The tibialresection block 112 has a universal design so that it may be used on theleft or right side of the knee, thereby minimizing the number of partsthat are required. The tibial resection block is preferably used toperform a tibial resection at a proximal end of a tibia. The tibialresection block desirably includes one or more holes 120 that mayreceive fasteners such as pins for securing the tibial resection blockto bone. One or more of the holes 120 may be adapted to secure a toolthereto, as will be described in more detail below. The tibial resectionblock also preferably includes one or more openings 122 adapted tosecure a navigation tracker for properly aligning the tibial resectionblock relative to the proximal end of a tibia.

The tibial resection block 112 also preferably includes a C-shapedopening 124 engagable with an elongated element such as a rod. After therod is coupled with the C-shaped opening 124, the tibial resection blockis designed to slide along the rod for adjusting the location of thetibial resection block relative to the proximal end of the tibia. Thetibial resection block 112 may also include a threaded opening 126aligned with the C-shaped opening 124. A tightening screw 128 hasthreads 130 that are preferably received within the threaded opening126. The tightening screw 128 also includes a lever 132 that may pivotabout a pivot point 134 for enabling greater leverage to be applied tothe tightening screw. The pivotable lever also preferably allows thescrew 128 and the lever 132 to remain below the resection surface.

Referring to FIGS. 3A-3D, the tibial resection block 112 is securable toa rod 136 having a proximal end 138 and a lower end (not shown). Thelower end of the rod may be connected to an ankle clamp for stabilizingthe rod. Referring to FIG. 3B, the rod 136 is preferably secured withinthe C-shaped opening 124 of the tibial resection block 112, with theinner contoured surface 116 facing the tibia and the outer contouredsurface 118 facing away from the tibia. The proximal end 138 of the rod136 includes a flange 140 having a pin opening 142 for anchoring the rodto the proximal end of a tibia so as to further enhance the stability ofthe rod 136 and the tibial resection block 112. The tibial resectionblock 112 also desirably includes one or more navigation trackeropenings 122 for properly aligning the tibial resection block with thesurface to be resected.

Referring to FIGS. 3A, 3C and 3D, after the top surface 114 of thetibial resection block 112 is positioned at a correct height relative tothe proximal end of the tibia, the lever 132 may be grasped fortightening the tightening screw 128 so as to lock the position of thetibial resection block relative to the rod 136.

Referring to FIG. 3C, in order to more firmly secure the position of thetibial resection block 112 relative to the proximal end of the tibia,one or more securing elements such as pins may be passed through theouter openings 120. The central openings 144 may be used for alignmentpins or for securing tools to the tibial resection block, such assecuring a stylus to the tibial resection block.

FIG. 4 shows a saggital resection alignment guide 146 that is securableto the tibial resection block 112 shown in FIGS. 2 and 3A-3D. Thesaggital resection alignment guide 146 preferably includes a main body148, an elongated rod 150 that slides through an opening in the mainbody and an alignment block 152 secured to an end of the elongated rod150. The alignment guide 146 also includes a depressible button 154 thatmay be depressed for allowing the rod 150 to move relative to the mainbody 148. The saggital resection alignment guide 146 may includeprojections, such as posts or hooks (not shown), that engage one or moreof the openings in the tibial resection block shown above in FIG. 2.

Referring to FIGS. 5A-5E, in certain preferred embodiments of thepresent invention, a modular handle 156 for inserting a combination burguide and spacer block includes a handle portion 158 having an upper endsecured to an alignment element 160 having a leading end 162 and atrailing end 164. The leading end 162 of the alignment element 160preferably includes a male projection 166 on one lateral side thereofand a pin 168 on an opposite side thereof. Modular handle 156 alsoincludes a male end connector 169 projecting from the second end 164 ofthe alignment element 160. The modular handle 156 also includes adepressible button 170 and a spring 172 coupled therewith. Thedepressible button 170 may be depressed for interacting with the pin168. In one button position, the pin 168 is free to move inwardly in pinopening 174. When the button 170 is not depressed, however, the pin islocked outwardly and may not retract within the opening 174.

Referring to FIGS. 6A-6H, in accordance with certain preferredembodiments of the present invention, a bur template/spacer block 176includes a bur template portion 178 for guiding burring of femoral boneand a spacer block portion 180 insertible into a knee joint. Referringto FIGS. 6A and 6E, the bur template/spacer block 178 includes a slot182 that defines an outer surface 184, an inner surface 186 and an apex188. The bur portion 178 includes an inner surface 190 and an outersurface 192. The inner and outer surfaces 190, 192 are preferably curvedto conform to the condyle at a distal end of a femur. The spacer portion180 includes a top surface 194 and a bottom surface 196 remotetherefrom. Depending upon the gap between the femur and the tibia, aplurality of spacer blocks may be provided having varying thicknesses.In certain preferred embodiments, spacer blocks are available havingthicknesses of between 4-14 mm and more preferably 6-12 mm. Referring toFIGS. 6C and 6G, the spacer block portion 176 has an opening 198extending from a trailing end of the spacer block toward a leading endof the spacer block. The opening 198 preferably has an elongatedalignment groove 200 extending along one side thereof. Referring toFIGS. 6F and 6H, the spacer block portion 180 has at least post opening202 extending between the top and bottom surfaces 194, 196. Referring toFIGS. GA and 6G, the outer rail 204 of the bur template portion 178includes pin fixation flanges 206A, 206B. The pin fixation flangesinclude openings extending therethrough that are adapted to receivesecuring elements such as pins so that the bur template may be anchoredto bone.

Referring to FIGS. 7A-7D, in accordance with certain preferredembodiments of the present invention, the system includes a shim 208having a posts 210 projecting from a first surface 212 thereof. The shim208 includes opposing sidewalls 214A, 214B. As will be described in moredetail below, the shim may be assembled over either the top surface orthe bottom surface of the spacer block portion of the burtemplate/spacer block shown in FIGS. 6A-6H for adjusting the position ofthe bur template/spacer block. The shim may also be used for adjustingthe thickness of the spacer block. In certain preferred embodiments,more than one shim may be connected with the spacer block.

Referring to FIGS. 8A-8E, in accordance with certain preferredembodiments of the present invention, the system includes an alignmenttower 216 that may be coupled with the modular handle shown in FIGS.5A-5E for inserting and aligning the bur template/spacer block in a kneejoint. Referring to FIGS. 8A, 8B and 8E, the alignment tower 216preferably includes a shaft 218 having an upper end 220 and a lower end222. Referring to FIGS. 8A-8E, the alignment tower includes an alignmentflag 224 secured to the upper end 220 of the shaft 218 and a connectionmember 226 secured to the lower end of the shaft 218. Referring to FIGS.8A and 8B, the alignment flag 224 includes a number of holes 228extending therethrough that are used for approximating the center of aknee. In certain preferred embodiments, an alignment rod can be passedthrough one or more of the holes 228 in the flag 224 for locating orapproximating the center of the knee. Referring to FIGS. 8A, 8B and 8D,the connection member 226 at the lower end includes a C-shaped opening230 having a centrally located well 232 and an elongated groove 234extending from opposite sides of the well 232. The central well 232 isadapted to fit over the male end connector 169 of the modular handle 158(FIGS. 5A-5E).

Referring to FIGS. 9A-9E, in accordance with certain preferredembodiments of the present invention, the system includes a posteriorresection guide locator 236. Referring to FIGS. 9A, 9B and 9D, theposterior resection guide locator includes an alignment rail 238 havinga first end 240 and a second end 242. The alignment rail 238 alsodesirably includes a first lateral surface 244 and a second lateralsurface 246 extending on opposite sides of the alignment rail 238between the first and second ends 240, 242 thereof. The alignment rail238 includes a first male projection 248 provided adjacent the first end240 and a second male projection 250 provided adjacent the second end242. The male projections 248, 250 are sized to fit into the elongatedalignment groove 200 (FIG. 6G) provided at the trailing end of thespacer block. The particular first end 240 or second end 242 of the rail238 that is inserted into the alignment groove 200 may depend upon thetype of operation being conducted. For example, the first end 240 may beinserted in the groove 200 for a LM/RL procedure and the second end 242may be inserted in the groove 200 for a RM/LL procedure.

Referring to FIGS. 9A-9E, the posterior resection guide locator 236includes a support element 252 and a pin guide 254 mounted atop thesupport element 252. The pin guide 254 preferably includes one or morepin holes 256 extending therethrough. As will be described in moredetail below, after the posterior resection guide locator is coupledwith the elongated alignment groove in the bur template/spacer blockshown in FIGS. 6A-6H, the pin holes 256 are aligned with the opening inthe bur template portion and alignment pins are inserted into bonethrough the pinholes 256. The alignment pins are preferably used toalign a posterior resection guide for conducting a posterior resectionof the femur, as will be described in more detail below.

Referring to FIGS. 10A-10D, in accordance with certain preferredembodiments to the present invention, the assembly includes a standardposterior resection guide 258 including a main body 260 having an upperend with pin holes 262 and a lower end with a slot 264 extendingtherethrough. The slot 264 is preferably a captured slot that is boundedon left and right sides thereof by the main body 260. As a result, acutting instrument such as a saw placed into the slot cannot extendbeyond the left and right boundaries of the main body. The posteriorresection guide also includes a ledge 266 that projects from one side ofthe slot 264. The combination of the ledge 266 and the captured slot 264control movement of a cutting blade so as to accurately control the cutthrough a posterior region of the femoral condyle. In certain preferredembodiments of the present invention, the standard posterior resectionguide 258 is sized and configured to remove 6 mm of bone from theposterior region of the femoral condyle, which matches the 6 mmthickness of the femoral component of the implant. The size andconfiguration of the standard posterior resection guide may be varied sothat the amount of bone to be removed matches the thickness of thefemoral component.

FIGS. 11A-11C show a posterior resection guide 258′, in accordance withanother preferred embodiment of the present invention. The posteriorresection guide 258′ is generally similar to the standard posteriorresection guide shown in FIGS. 10A-10D, however, it includes threedifferent sets of pin holes. The first set of pin holes 268′ is used forperforming a standard posterior resection, which is certain preferredembodiments is 6 mm. A second set of pin holes 270′ is used when theresection guide must be lowered when performing a posterior resectionfor reducing the amount of bone removed from the posterior region of thefemur. A third set of pin holes 272′ is used when the resection guidemust be raised when performing a posterior resection for increasing theamount of bone removed from the posterior region of the femur. As willbe described in more detail below, it may be necessary to raise or lowerthe posterior resection guide 258′ from a standard resection (e.g.removing 6 mm of bone from the posterior region of the femoral condyle)in order to balance the gap of a knee joint when in an extended positionand a flexed position. The posterior resection guide may be raised orlowered so that the gap in extension is equal to the gap in flexion andvice versa. As is well known to those skilled in the art, uneven gapsmay result in flexion instability or extension instability.

Referring to FIGS. 12A-12F, in certain preferred embodiments of thepresent invention, the system includes a femoral trial cutting guide 274for preparing the distal end of the femur to receive the femoralcomponent of the implant. The femoral trial cutting guide 274 desirablyincludes a set of anchoring pins 276 projecting from an inner face 278thereof. The cutting guide 274 also desirably includes a central opening280 extending therethrough and an elongated slot 282 that intersects thecentral opening 280. The elongated slot preferably extends between upperand lower ends of the cutting guide 274. After the condyle at the distalend of a femur has been burred using the bur template portion of the burtemplate/spacer block shown above, the inner face 278 of the cuttingguide 274 is abutted against the burred surface of the femur. The pins276 are preferably inserted into bone for holding the cutting guide inplace. An impactor may be used to advance the anchor pins 276 into thebone. A drill may be inserted through the central opening 280 to form apost opening for an implant peg. In addition, a cutting instrument, suchas a saw or cutting blade, may be inserted through the elongated slot282 to form a keel opening for an implant.

Referring to FIG. 12B, the cutting guide 274 preferably has an outersurface that is curved. The curved outer surface of the cutting guidemay be used to perform a range of motion test. After the post and keelopenings have been formed, and a range of motion test is completed, thecutting guide 274 may be removed from its attachment to the femoralbone.

Referring to FIG. 13A, in certain preferred embodiments, the systemincludes a drill guide 286 having a first end 288 with a threadedprojection 290 and a second end 292 including a handle. Referring toFIGS. 14A-14E, the drill guide 286 has a central opening 294 extendingbetween the first end 288 and the second 292. The opening 294 includes areduced diameter area or shelf 296 that limits forward movement of adrill. Referring to FIGS. 13A-13B and 14C, after the threaded projection290 of the drill guide 286 is threaded into central opening 280 of thecutting guide 274, a drill bit 298 may be passed through the opening 294of the drill guide 286 until a portion of the drill abuts against theshelf 296 for limiting further advancement of the drill bit 298. Thedrill may be operated for forming a post opening in the femoral bone.The post opening, as will be described in more detail below, is adaptedto receive a post of a permanent femoral component of an implant. Afterthe post hole has been formed, the drill bit 298 may be removed from thedrill guide 286. The handle 292 of the drill guide may be grasped toremove the cutting guide 274 from its attachment to the femoral bone. Incertain preferred embodiments, the drill guide 286 may be used as animpaction/extraction handle for a trial such as a femoral trial.

Referring to FIGS. 15A-15D, in accordance with certain preferredembodiments of the present invention, the system includes a punch tower300 for forming keel openings in tibial bone. Referring FIG. 15A, thepunch tower 300 includes a main body 302 having a leading end 304 and atrailing end 306. The punch tower 300 includes a latch paw 308 securableto the main body 302. The latch paw includes an opening 310 extendingtherethrough that is adapted to receive a pivot pin 312 so that thelatch paw may be coupled with the main body 302 and pivot relativethereto. The latch paw also includes a spring 314 that normally urgesthe latch paw to move downwardly at its hooked front end 316. The punchtower also preferably includes an alignment flange 318 that may becoupled with a trailing end 306 of the main body 302. The alignmentflange includes one or more openings 320 extending therethrough that areadapted to receive pins for anchoring the punch tower to bone. Thealignment flange 318 desirably includes a C-shaped opening 322 at anupper end thereof that is adapted to slide over a rail 324 at thetrailing end 306 of the main body 302. A pin 312 is disposed inengagement with the alignment flange 318 to secure the alignment flangewith the main body 302.

The main body 302 preferably includes a series of slots 326 extendingtherethrough. The series of slots 326 are adapted for forming differentsized keel openings in tibial bone. Referring to FIG. 15A, a first slot126A is used for forming a small keel opening, a second slot 126B isused for forming a medium keel opening and a third slot 126C used forforming a large keel opening. In other preferred embodiments, more thanthree slots may be provided.

Referring to FIGS. 15B and 15C, an underside of the main body 302includes an alignment guide 328 at the leading end 304 thereof. Thealignment guide 328 includes male projections 330 extending alongopposite sides of the main body.

Referring to FIG. 16A, the leading end 304 of the main body 302 isadapted to be coupled with a tibial template 332 having an elongatedopening 334. The elongated opening 334 includes female grooves 336extending along a longitudinal axis of the tibial template 332. The maleprojections 330 provided at the underside of the main body 332 areadapted to slide into the female grooves 336 in the tibial template 332.

Referring to FIGS. 16A-16C, the assembly includes a chisel 338 that isinsertible into one of the slots 326 in the punch tower. The assemblyalso includes a tamp 340 that slides within the chisel 338, as will bedescribed in more detail below. FIGS. 16B and 16C show the leading end304 of the punch tower coupled with the tibial template 332. As shown inFIG. 16B, the chisel 338 and tamp 340 are guided along an axis thatintersects an axis extending between the leading 304 and trailing 306ends of the main body 302.

Referring to FIGS. 17A-17D, the chisel 338 preferable includes a leadingend 342 and a trailing end 344. The leading end preferably includes asharpened surface 346 that cuts into bone. The trailing end 344desirably includes a striking surface 348 so that the chisel 338 may behit with a hammer or mallet. The second end 344 includes a handle 350having a shoulder 352 that limits advancement of the chisel 338 into theslot of the punch tower. The exact positioning of the shoulder 352 maybe varied in response to the depth of the bone cut required to be formedin the tibial bone.

Referring to FIGS. 17C-17D, the chisel includes a C-shaped opening 354extending along the length thereof. The C-shaped opening provides aspace for bone to move when the keel opening is being formed. TheC-shaped opening 354 also provides a space for a tamp, as will bedescribed in more detail below.

Referring to FIGS. 18A-18D, in accordance with certain preferredembodiments of the present invention, the system includes a tamp 340having a leading end 356 and a trailing end 358 including a handle 360.Referring to FIG. 18C, the handle 360 includes a shoulder 362 thatpreferably abuts against the striking surface 348 of the chisel 338(FIG. 17A) for limiting advancement of the tamp 340. After the chiselhas been advanced into bone for forming an outline of the keel opening,the tamp is advanced through the chisel to impact the bone and completethe formation of the keel opening.

Referring to FIGS. 19 and 21A, the tibial template 332 preferablyincludes a central opening 334 having opposing female slots 336extending between a leading end 362 and a trailing end 364 thereof. Thetibial template includes a first slot 366 for receiving a hooked end ofa latch paw when the template is used on one side of a knee and a secondslot 368 that is also designed to receive the hooked end of a latch pawwhen the template is flipped over. The tibial template 332 alsodesirably includes one or more openings 370 extending between top andbottom surfaces 372, 374 thereof, which are adapted to receive anchorpins for anchoring the tibial template to the proximal end of the tibia.

FIG. 20 shows a holder 380 for holding different sized tibial templates.The holder preferably includes a first arm 382 for holding an extrasmall or small sized tibial template 332A, a second arm 384 for holdinga medium or large sized tibial template 332B and a third arm 386 forholding an extra large sized tibial template 332C. Each arm of theholder 380 has an outer end including an opening 388 that is the size ofa keel opening for the particular implant part to be implanted intobone. Thus, the opening 388A in the first arm 382 is smaller than theopening 388B in the second arm 384 and so on.

FIGS. 22A-22D show a spacer bar 390, in accordance with certainpreferred embodiments of the present invention. The spacer bar 390includes a first section 392 defining a height H₁ and a second section394 defining a height H₂ that is greater than H₁. In certain preferredembodiments, the difference between H₁ and H₂ is preferably thethickness of the implant that is positioned between the posteriorcondyle and the tibia. The spacer bar includes a first end 396 that istapered and a second end 398 that is also tapered. As will be describedin more detail below, the spacer bar is placed between the distal end ofa femur and a proximal end of a tibia to determine spacing between thefemur and tibia during extension and flexion of the knee joint. Thespacer bar may be used to align a cutting instrument for cutting theposterior region of the femur. As described herein, it is preferablethat the gap between the femur and the tibia is the same for bothflexion and extension. Thus, the present invention seeks to prepare bonesites and attached implant components to the respective bone sites sothat the gap between the femur and tibia is the same in both flexion andextension so as to reduce joint instability and provide for smoothmovement between flexion and extension.

FIGS. 23-32 show a preferred method of preparing a seating surface at aproximal end of a tibia. Referring to FIG. 23, a tibial resection block112 is coupled with an elongated rod 136. Referring to FIG. 24, theattachment flange 140 at the proximal end 138 of the rod 136 is securedto the proximal end 102 of the tibia 104 using a fastener 145 such as apin. A lower end (not shown) of the rod 136 is preferably secured to thetibia 104 such as by using an ankle clamp.

Referring to FIG. 25, the tibial resection block 112 has a top surface114 that defines a cutting plane for the proximal end 102 of the tibia104. A stylus 141 is preferably coupled with the tibial resection blockso as to determine a depth of cut into the proximal end 102 of the tibia104. The tibial resection block 112 may slide along the rod 136 untilthe desired position of the top surface 114 of the block 112 isdetermined. At that point, the tightening screw 128 is tightened forsecuring the position of the tibial resection block 112 along the rod136. In other preferred embodiments, the tibial resection block may becoupled with a navigation tracker for aligning the top surface 114 ofthe block 112 at the appropriate depth for the resection.

Referring to FIG. 26, anchoring pins 143 may be passed through openingsin the tibial resection block 112 to further stabilize the tibiaresection block relative to the tibia. Referring to FIG. 26, a saggitalresection guide 146 may be moved into abutment against the tibialresection block 112.

Referring to FIG. 27, the saggital resection guide 146 has a main body148 that is abutted against the tibial resection block 112. Thedepressible button 154 of the saggital resection guide 146 may bedepressed to allow movement of the alignment block 152 for defining asaggital cutting plane between the alignment block 152 and the proximalend 138 of the rod 136. The outer surface of the alignment block 152 maybe rounded to provide for a perpendicular cut of the bone.

Referring to FIGS. 28 and 29, a saw 149 or other cutting instrument maybe used to make a saggital resection of the proximal end 102 of thetibia 104. Referring to FIG. 30, a second cutting instrument or saw 151may be used to cut the proximal end 102 of the tibia 104 in a planedefined by the top surface 114 of the tibial resection block 112. FIGS.31 and 32 show the proximal end 102 of the tibia 104 after the tibialresection if complete. The tibial resection block may then be disengagedfrom the tibia.

FIGS. 33-37 show femoral alignment of the bur template/spacer blockwithin the knee joint. The leading end 162 of the modular handle 158shown in FIGS. 5A and 6G is coupled with the female opening 198 of thebur template/spacer block. The male projection 166 at the leading end162 of the modular handle 158 is preferably inserted into the elongatedalignment groove 200 in the opening 198 at the trailing end of thespacer block portion 176. A shim may be coupled with the spacer blockfor adjusting for the gap distance in the knee.

Referring to FIG. 34, the alignment tower 216 shown in FIG. 8A iscoupled with the male projection 169 of the modular handle 158 (FIG.5A). The male projection 169 of the modular handle is preferably coupledwith the well 232 at the bottom of the alignment post 216. Referring toFIGS. 35-37, the spacer block portion 180 of the bur template/spacerblock is inserted into the joint between the distal end 106 of femur 108and the proximal end 102 of tibia 104. An alignment rod is desirablyplaced in the appropriate hole in the alignment tower 216 which ispreferably centered on the knee or on the femur using openings 228 inthe alignment flag 224 (FIG. 8A). Referring to FIG. 37, once the spacerblock 180 is in place, the tibia is extended until the curved innersurface 190 of the bur template engages the femoral condyle. Once theentire length of the curved inner surface of the bur template engagesthe femoral condyle, extension of the knee joint may be stopped. At thatstage, the bur template is preferably secured from further movementrelative to the femur using fasteners such as anchoring pins.

Referring to FIG. 38, the one or more pins for anchoring the burtemplate from further movement relative to the femur may be insertedthrough securing flanges 206A, 206B. In the particular preferred FIG.38, a shim 208 is coupled with an underside of the spacer block foradjusting the tension of the bur template/space block in the joint. Aswill be described in more detail herein, the shim may be used forbalancing the gap between the femur and the tibia when the knee jointmoves between flexion and extension. A bur (not shown) may be insertedinto the slot 182 of the bur template/spacer block to prepare thecondyle at the distal end of the femur for receiving a femoral componentof the implant.

Referring to FIGS. 9A and 39, the alignment rail 238 of the posteriorresection guide locator 236 is preferably inserted into the opening atthe trailing end of the bur template/spacer guide 176. The projection248 on the alignment rail 238 is preferably inserted into the elongated,alignment groove 200 (FIG. 6G) in the spacer block. Referring to FIG.39, once the alignment rail is inserted into the opening in the spacerblock, the pin openings 256 of the posterior resection guide locator 236are preferably in alignment with the slot 182 of the bur template/spacerblock 176. Referring FIGS. 39 and 40, a pair of alignment pins 153 aredesirably inserted through the pin openings in the posterior resectionguide locator 236 and advanced into the bone at the distal end of thefemur. In certain preferred embodiments of the present invention, theguide locator 236 is preferably sized and shaped so that the alignmentpins 153 are attached to the femur at a location that will eventuallyresult in 6 mm of bone being resected from the posterior region of thefemur.

Referring FIGS. 40 and 41, a posterior resection guide 258 is alignedwith the femur 108 using the previously anchored alignment pins 153.Referring to FIGS. 41 and 42, a posterior resection of the femur isdesirably performed by passing a cutting instrument such as a saw 155through the slot 264 in the posterior resection guide 258. The posteriorresection guide is sized and shaped so that it slides over the alignmentpins that were previously anchored in the bone using the posteriorresection guide locator. The posterior resection guide is preferablysized and shaped so that once it is slid over the alignment pins 153,the slot is located so that a predetermined section of bone from theposterior region of the femur is removed. In certain preferredembodiments, the posterior resection guide is sized and shaped so that 6mm of bone is removed from the posterior region of the femur. As shownin FIG. 43, after the posterior resection of the femur 108 is complete,the posterior resection guide and the alignment pins are removed.

Referring to FIGS. 44 and 45, a tibial template 332 may be positionedover the prepared site at the proximal end 102 of the tibia 104. Thesurgeon desirably makes a determination of the proper sized tibialtemplate that should be used, which is based upon the area of theprepared site at the proximal end of the tibia. The tibial template ispreferably used to prepare the site for receiving a tibial component ofan implant.

Referring to FIGS. 46 and 47, after the proper tibial template has beenselected, the leading end 304 of the punch tower 300 is coupled with theopening in the tibial template. As described above, the male projectionsat the leading end 304 of the punch tower 300 slide into the femaleopenings in the elongated opening of the tibial template. The latch paw308 desirably engages a latch paw groove formed in the top surface ofthe tibial template for securing the tibial template and the punch towertogether.

Referring to FIGS. 48 and 49, the coupled together tibial template andpunch tower are preferably moved into place over the prepared site atthe proximal end of the tibia. Referring to FIG. 49, a pin may be usedto anchor the tibial template and/or the punch tower to the bone.

Referring to FIG. 50, addition pins may be passed through the attachmentflange 318 of the punch tower to further anchor the punch tower to bone.

Referring to FIGS. 51-53, after the punch tower and tibial template havebeen anchored to the tibia, the chisel is desirably passed through anappropriate slot in the punch tower and hammered in place using a hammeror mallet. As shown in FIG. 51, the punch tower 300 has at least threeslots for receiving the chisel 338. As noted above, each of the threeslots will result in the formation of keel opening having a particularsize. FIG. 53 shows the chisel 338 after it has been fully advanced inthe punch tower 300.

Referring to FIGS. 54 and 55, the tamp 340 is then hammered in placethrough the chisel 338 to complete formation of the keel opening.Referring to FIG. 56, the punch tower is then removed. A keel openinghas been formed at the prepared site at the proximal end of the tibia.

FIG. 57 shows a prepared site at the distal end 106 of the femur 108,which has been prepared by passing a bur through the slot in the burtemplate/spacer block shown and described above in FIGS. 6A-6H.Referring to FIG. 58, in order to prepare the distal end of the femurfor receiving a femoral component of the implant, a femoral trialcutting guide, such as that shown and described above in FIGS. 12A-12Fand 13A, is abutted against the prepared site. The outer perimeter ofthe femoral trial cutting guide 274 desirably matches the perimeter ofthe prepared site previously burred on the femur. The cutting guide ispreferably handled by attaching the drill guide 286 to the cuttingguide.

Referring to FIG. 58, after the cutting guide is in place, a drill bitmay be passed through an elongated opening in the drill guide 286 toform a post opening for the implant. Referring to FIG. 59, a cuttinginstrument, such as a saw, may be passed through the elongated slotformed in the cutting guide 274 so as to form an elongated opening for akeel on an implant.

FIGS. 60-62 show a prior art bur template used to prepare the distal endof a femur for receiving an implant. As is well known to those skilledin the art, the template generally conforms to the shape of an actualimplant. Thus, it is important that the template conform to the shape ofthe distal end of the femur as closely as possible. Referring to FIG.61, after the posterior region of the femoral condyle has been resected,and while the leg remains flexed, the upper part of the bur template isabutted against the condyle at the distal end of the femur. As shown inFIG. 61, a gap forms between the prepared site at the posterior regionof the femur and the template. This may result in a number of problemsincluding a poor fit between the implant and the distal end of thefemur, joint instability or the removal of excessive bone from thedistal end of the femur in order to fit the implant to the femur bone.Conversely, referring to FIG. 62, if the lower end of the bur templateis placed in contact with the prepared site at the posterior region ofthe femur, the upper part of the bur template is spaced from the condyleof the femur. This may cause a number of problems including a poor fitbetween the implant and the femur bone, joint instability and/or theremoval of excessive bone from the femur in order to fit the implant tothe femur bone. In certain preferred embodiments, the present inventionseeks to avoid these problems by preparing the site at the distal end ofthe femur before removing bone from the posterior region of the femur.In other preferred embodiments, the present invention seeks to minimizethe amount of bone removed from the posterior region of the femur whenbalancing the gaps between the femur and the tibia when the joint movesbetween an extended position and a flexed position.

FIGS. 63A and 63BB show a knee joint in an extended position, after thetibia has been resected but before the femur is resected. A spacer bar,similar to that shown in FIGS. 22A-22D, is placed in the gap between thedistal end 106 of the femur 108 and the proximal end 102 of the tibia104. The spacer bar is used to measure the distance or gap between thedistal end of the femur and the prepared site at the proximal end of thetibia. Referring to FIGS. 64A and 64B, the knee joint is then flexed andthe gap between the posterior region of the femur and the prepared siteat the proximal end of the tibia is measured. Ideally, the gap betweenthe femur and tibia is the same when the joint is in the extended andflexed positions. For example, in certain instances, the gap when thejoint is flexed is 6 mm and the gap when the joint is extended is 6 mm.Often, however, the gap distances change as the joint moves betweenextended and flexed positions. For example, the flexion gap may be 8 mmand the extension gap may be 6 mm. Thus, certain preferred embodimentsof the present invention seek to balance the gap between the femur andthe tibia so that the gap in extension is equal to the gap when the kneeis flexed. Unlike prior art methods, certain preferred embodiments ofthe present invention seek to balance the gaps by taking more or lessbone from the posterior region of the femur, rather than by takingadditional bone from the distal end of the femur. Moreover, in certainpreferred embodiments, the posterior resection of the femur takes placeonly after the site at the distal end of the femur has been completelyprepared. In still other preferred embodiments, although some bone maybe removed from the posterior region before the distal end of the boneis burred, the final posterior resection region is not completed untilthe site at the distal end of the femur is finalized.

Referring to FIGS. 63A and 63B, the extension gap between the distal endof the femur and the prepared site at the proximal end of the tibia isabout 6 millimeters. Referring to FIGS. 64A and 64B, the flexion gapbetween the posterior region of the femur and the prepared site at theproximal end of the tibia is about 8 millimeters. Thus, the gap is 2 mmlarger in flexion than in extension. The present invention seeks tobalance the gaps so that the gap in flexion is equal to the gap inextension. In certain preferred embodiments, the present inventionbalances the gap by decreasing the flexion gap by 2 millimeters, ratherthan increasing the extension gap by 2 millimeters. As a result, lessbone is removed from the femur.

FIG. 65 shows a gap balancing table that may be used for calculating theamount of bone that is removed from the posterior condyle of the femur.The table may be used by a surgeon for balancing the flexion andextension gaps of a knee joint. As noted above, use of the tablepreferably minimizes the amount of bone that is removed from the femur.Use of the table also preferably results in proper positioning of theimplant parts on the femur and the tibia and smooth movement of the kneejoint when moving between the extended and flexed positions. Forpurposes of clarity, the table uses 6 mm as the preferred gap for a kneejoint in both flexion and extension. This chart also assumes that thethickness of the femoral component of the implant is 6 mm. In otherpreferred embodiments, other thicknesses may be used, e.g. 4 mm, 8 mm,etc. If the initial gap distance is more or less than 6 mm, then more orless bone is removed from the posterior region of the femoral condyle sothat the final gap distance in extension is the same as the final gapdistance in extension.

Referring to the table, the gap distance associated with a tight fit is4 mm; the gap distance associated with a good fit is 6 mm and the gapdistance associated with a loose fit is 8 mm. The table includes a firstrow that compares a tight extension gap (4 mm) with a tight (4 mm), good(6 mm) and loose (8 mm) flexion gap. If the extension gap and theflexion gap are both tight, then the gap is considered to be in balanceand the standard 6 mm of bone is removed from the posterior condyle. Ifthe extension gap is tight (4 mm) and the flexion gap is good (6 mm),then the gaps are not in balance. In order to balance the gaps, 2 mmless bone material is removed from the posterior region of the femoralcondyle for a total of 4 mm (6 mm−2 mm=4 mm) of bone being removed. Ifthe extension gap is tight (4 mm) and the flexion gap is loose (8 mm),then the gaps are not in balance and 4 mm less bone material is removedfrom the posterior region of the femoral condyle for a total of 2 mm (6mm−4 mm=2 mm) of bone being removed.

The second row of the gap balancing table is used when the extension gapis good (e.g. 6 mm). If the extension gap is good (6 mm) and the flexiongap is tight (4 mm), then the gaps are not in balance. In order tobalance the gaps, 2 mm of additional bone is removed from the posteriorregion of the femoral condyle for a total of 6 mm (4 mm+2 mm=6 mm) ofbone being removed. If the extension gap and the flexion gap are bothgood, then the gap is considered to be in balance and the standard 6 mmof bone is removed from the posterior region of the femoral condyle. Ifthe extension gap is good (6 mm) and the flexion gap is loose (8 mm),then the gaps are not in balance and 2 mm less bone is removed from theposterior region of the femoral condyle for a total of 6 mm (8 mm−2 mm=6mm) of bone being removed.

The third row of the gap balancing table is used when the extension gapis loose (e.g. 8 mm). If the extension gap is loose (8 mm) and theflexion gap is tight (4 mm), then 4 mm of additional bone is removedfrom the posterior region of the femoral condyle for a total of 8 mm (4mm+4 mm=8 mm) of bone being removed. If the extension gap is loose (8mm) and the flexion gap is good (6 mm), then 2 mm of additional bone isremoved from the posterior region of the femoral condyle for a total of8 mm (6 mm+2 mm=8 mm) of bone being removed. If the extension gap isloose (8 mm) and the flexion gap is loose (8 mm), then the gap isbalanced and the standard 6 mm (6 mm+0 mm=6 mm) of bone is removed fromthe posterior region of the femoral condyle and the 8 mm tibialcomponent is preferably used.

In FIG. 66, the flexion gap is 8 mm and the extension gap is 6 mm sothat the flexion gap is 2 mm greater than the extension gap. Thus, astandard 6 mm posterior resection will result in a flexion instabilityof 2 mm. This is shown in FIG. 66 where reference line 425 designatesthe cut line for a standard 6 mm posterior resection and line 435 is 6mm away from line 425 (the thickness of the femoral component of theimplant). When the femoral component 440 is attached to the bone, theouter surface 440 is present at line 435. However, an 8 mm flexion gapstill remains between the proximal end of the tibia (designated by line445) and the outer surface of the implant (designated by line 435).Thus, in order to balance the flexion gap with the extension gap, theposterior resection must be lowered by 2 mm so that the outer surface ofthe implant is lowered by 2 mm. Lowering the femoral component by 2 mmwill result in a 6 mm flexion gap and a 6 mm extension gap. As a result,when the femoral component 440 shown in FIG. 66 is attached to thedistal end of the femur 108, the outer surface 442 of the implant 440will form a flexion gap of 6 mm.

Adjusting the posterior resection is shown in conjunction with FIGS.67-69. Referring to FIG. 67, after the bur template/spacer block hasbeen positioned between the knee joint and pinned to the femur, thealignment rail of the posterior resection guide locator 236 is insertedinto the alignment opening of the bur template/spacer block 176. Pins153 are then passed through the pin openings of the posterior resectionguide locator and into the distal end of the femur bone. As shown inFIGS. 39-40, the posterior resection guide locator 236 is then removedso that only the pins 153 remain attached to the bone. Referring toFIGS. 40-43 and 68, if the flexion gap matches the extension gap, thenthe standard posterior resection guide 258 may be used to provide a 6 mmposterior resection. The prepared site with the 6 mm posterior resectionis shown in FIG. 43.

If the flexion gap does not match the extension gap, then the posteriorresection must be adjusted from the standard 6 mm cut as discussed abovewith reference to the gap balancing table of FIG. 65. This may beaccomplished by using a second posterior resection guide 258′, shown inFIG. 69, having three sets of pin openings. Although three sets of pinopenings are shown, it is contemplated that other preferred embodimentsmay have four or more sets of pin openings for further modification ofthe amount of bone removed during a posterior resection. The middle setof openings 268′ provides for a standard posterior resection of 6 mm ofbone. The upper set of openings 270′ lowers the posterior resectionguide 258′ by 2 millimeters so that the posterior resection removes 4 mmof bone. In certain preferred embodiments, the upper set of openings270′ is used when the flexion gap is greater than the extension gap. Theposterior resection guide 258′ also includes a lower set of openings272′ that is used when the posterior resection must be raised by 2 mm.The third set of openings 272′ may be used when the flexion gap is lessthan the extension gap. In other preferred embodiments, the sets ofopenings may be 1 mm apart, or another desired distance.

Referring to FIG. 70A, line 425 shows the standard posterior resectionof 6 mm of bone. Line 435 shows a posterior resection that has beenlowered 2 mm so that only 4 mm of bone is removed. Line 455 shows theburred surface 455 formed at the femoral condyle 110 at the distal endof the femur 108, with the inner surface of the femoral component of theimplant being shown at line 442. Due to downward shifting of the femoralcomponent by about 2 mm (preferably after the distal burring isaccomplished), a gap may form between the burred surface 455 and theinner surface 442 of the femoral component. Referring to FIG. 70B, bonecement 460 may be used for filling the gap resulting from the downwardshifting of the femoral component.

In other preferred embodiments of the present invention, the amount ofbone removed during the posterior resection may be controlled bycoupling a shim with the spacer block portion of the bur template/spacerblock. The shim may be coupled with either the top surface of the spacerblock or the bottom surface of the spacer block. FIG. 71 shows the burtemplate/spacer block 176 of FIG. 6A aligned for assembly with shim 208of FIG. 7A. Shim 208 includes a post 210 that is insertible in anopening extending through spacer block 180. In FIG. 71, the shim isoriented for assembly with a bottom surface of the spacer block. In FIG.72, the shim 208 is oriented for assembly with a top surface of thespacer block 180.

Referring to FIG. 73, the shim 208 having a thickness of 2 mm isassembled with the top surface of the spacer block 180. The addition ofthe 2 mm shim on top of the spacer block lowers the posterior resectionby 2 mm. As a result, when the standard posterior resection guide 258 ofFIG. 68 is slid over the pins shown in FIG. 40 and the resectionconducted, only 4 mm of bone is removed from the posterior region,rather than the standard 6 mm.

Referring to FIG. 74, when the implant 440 is attached to the preparedsite on the femur 108, the gap between the outer surface 442 of theimplant 440 and the upper prepared surface of the tibia 104 is 6millimeters. This 6 millimeter gap in flexion is the same distance asthe 6 mm extension gap.

FIGS. 75 and 76 show a knee joint having a flexion gap that is less thanthe extension gap. In order to balance the gaps, the posterior resectionmust be raised by a particular distance. FIG. 75 shows a standard 6millimeter posterior resection line 470 that may be formed using thestandard posterior resection guide 258 shown in FIG. 68. When theimplant 440 is attached to the distal end of the femur, the outersurface 442 of the implant defines a tangent line 472 that is 4 mm fromline 474. In this case, a 2 mm extension instability exists. Correctingthis situation requires the posterior resection to be raised 2 mm sothat the flexion gap matches the extension gap.

Referring to FIG. 76, in order to raise the outer surface of the implant2 mm, the posterior resection line is first raised 2 mm to line 471. Asa result, when the implant 440 is attached to bone, the flexion gapbetween the outer surface 442 of the implant part 440 and the preparedsurface of the tibia is 6 millimeters, which matches the 6 millimeterextension gap.

After the sites have been prepared at the distal end of the femur andthe proximal end of the tibia, a femoral component of the implant isconnected with the distal end of the femur and a tibial component of theimplant is connected to the proximal end of the tibia. Referring toFIGS. 77A and 77B, the femoral component 440 has an outer surface 442that is preferably curved and an inner surface 444. The femoralcomponent 440 also preferably includes a post 446 projecting from theinner surface 444 and a keel 448 projecting from the inner surface 444thereof. The femoral component 440 is assembled with the distal end ofthe femur by abutting the inner surface 444 against the femoral bone.The post 446 and the keel 448 are preferably pressed into openingspreviously formed in the bone as described above with respect to thefemoral trial cutting guide shown in FIGS. 57-59.

Referring to FIGS. 78A and 78B, the implant includes a tibial component482 having a top surface 484 adapted to abut against the outer surface442 of the femoral component 440 (FIG. 77A). The tibial component 482includes an underside 486 having a keel 488 projecting therefrom. Thekeel is adapted to be inserted into a keel opening, such as the keelopening shown in FIG. 56.

Referring to FIG. 79, after final insertion of the implant, the outersurface 442 of femoral component 440 engages the top surface 484 oftibial component 482. The opposing outer surfaces of the two implantparts engage one another as the knee joint moves between a flexedposition and an extended position. In certain preferred embodiments, thefemoral and tibial components 440, 482 may be secured using cement. Inparticular preferred embodiments, the cement is applied over the post446 and keel 448 of the femoral component 440 shown in FIG. 77A. Cementmay also be applied over the bottom surface 486 and the keel 488 of thetibial component 482 shown in FIG. 78B. The first and second implantparts may be impacted into place just by using a striking instrumentsuch as a hammer, an impactor or a mallet. Any excessive cement presentaround the implant parts 440, 482 is preferably removed.

Disclosed herein are unicondylar knee implants, surgical instruments andprocedures in accordance with certain preferred embodiments of thepresent invention. It is contemplated, however, that the implants,instruments and procedures may be slightly modified, and/or used inwhole or in part and with or without other instruments or procedures,and still fall within the scope of the present invention. Although thepresent invention may discuss a series of steps in a procedure, thesteps can be accomplished in a different order, or be used individually,or in subgroupings of any order, or in conjunction with other methods,without deviating from the scope of the invention.

While there has been described and illustrated herein embodiments ofunicondylar knee implants and insertion methods therefor, it will beapparent to those skilled in the art that variations and modificationsare possible without deviating from the broad spirit and principle ofthe present invention. The present invention shall, therefore, not belimited solely to the specific embodiments disclosed herein and otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. A method of preparing a knee joint for receiving a unicondylar kneeimplant comprising: preparing a first seating surface at a proximal endof a tibia; providing a combination bur template and spacer block, saidbur template having an upper end, a lower end and a curved surfaceextending between the upper and lower ends thereof that is adapted toconform to a femoral condyle of a femur and said spacer block extendingfrom the lower end of said bur template and having top and bottomsurfaces; flexing said knee joint so that said prepared first seatingsurface at the proximal end of said tibia opposes a posterior region ofsaid femoral condyle; inserting said combination bur template and spacerblock into said knee joint so that the top surface of said spacer blockengages the posterior region of said femoral condyle and the bottomsurface of said spacer block engages the first seating surface at theproximal end of said tibia; while maintaining said spacer block betweensaid femur and said tibia, extending said knee joint until the curvedsurface of said bur template engages a distal region of said femoralcondyle; anchoring said bur template to the distal region of saidfemoral condyle and using said bur template to guide burring of thedistal region of said femoral condyle for preparing a second seatingsurface on said femur; after burring the distal region of said femoralcondyle, resecting the posterior region of said femoral condyle.
 2. Themethod as claimed in claim 1, wherein the preparing a first seatingsurface includes resecting the proximal end of said tibia.
 3. The methodas claimed in claim 1, wherein said bur template and said spacer blockare integrally connected together.
 4. The method as claimed in claim 1,wherein said bur template and said spacer block are permanentlyconnected together.
 5. The method as claimed in claim 4, wherein saidbur template and said spacer block form a single, rigid element.
 6. Themethod as claimed in claim 1, further comprising: determining a distancebetween the first seating surface on said tibia and the posterior regionof said femoral condyle; selecting one of a plurality of combination burtemplate and spacer blocks for inserting into said knee joint, theselected one having a spacer block thickness that matches the determineddistance between the first seating surface on said tibia and theposterior region of said femoral condyle.
 7. The method as claimed inclaim 1, wherein said combination bur template and spacer block includesan alignment feature formed in a trailing end of said spacer block, themethod further comprising inserting an alignment rail of a posteriorresection guide locator into the alignment feature formed in thetrailing end of said spacer block.
 8. The method as claimed in claim 7,said posterior resection guide locator includes at least one pin openingthat overlies said alignment rail of said posterior resection locatorguide, wherein said at least one pin opening is aligned with said burtemplate when said alignment rail is inserted into said alignmentfeature formed in said spacer block.
 9. The method as claimed in claim8, further comprising insetting a pin through said at least one pinopening and anchoring said at least one pin in said femur.
 10. Themethod as claimed in claim 9, further comprising disengaging saidposterior resection guide locator from engagement with said combinationbur template and spacer guide and sliding a posterior resection guideover said at least one pin in said femur.
 11. A method of preparingseating surfaces in a knee joint for receiving a unicondylar kneeimplant comprising: preparing a first seating surface for receiving atibial component at a proximal end of a tibia; flexing said knee jointso that said first seating surface opposes a posterior region of saidfemoral condyle; providing a combination bur template and spacer blockincluding said bur template having a curved surface extending betweenupper and lower ends thereof and said spacer block extending from thelower end of said bur template; inserting said spacer block into saidknee joint so that said spacer block engages the posterior region ofsaid femoral condyle and said first seating surface on said tibia; andwhile maintaining said spacer block between said femur and said tibia,extending said knee joint until the curved surface of said bur templateengages a distal region of said femoral condyle.
 12. The method asclaimed in claim 11, further comprising using said bur template to guideburring of the distal region of said femoral condyle for preparing asecond seating surface for receiving a femoral component.
 13. The methodas claimed in claim 12, after the preparing a second seating surfacestep, anchoring one or more alignment pins in the femoral bone at thesecond seating surface.
 14. The method as claimed in claim 13, using theone or more alignment pins anchored in the femoral bone for aligning aposterior resection guide with the posterior region of said femoralcondyle and using said posterior resection guide for resecting theposterior region of said femoral condyle.
 15. A kit for preparing a kneejoint for receiving a unicondylar knee implant comprising: a combinationbur template and spacer block comprising: a bur template having an upperend, a lower end and a curved inner surface extending between the upperand lower ends thereof; a spacer block extending from the lower end ofsaid bur template, said spacer block having a top surface, a bottomsurface, a leading end for insertion into a knee joint and a trailingend spaced from the leading end and adjacent the lower end of said burtemplate, wherein the trailing end of said spacer block includes anopening with an alignment feature that extends from the trailing end ofsaid spacer block toward the leading end of said spacer block.
 16. Thekit as claimed in claim 15, further comprising a posterior resectionguide locator including an alignment rail insertible into the opening atthe trailing end of said spacer block.
 17. The kit as claimed in claim16, wherein the alignment rail is adapted to mesh with the alignmentfeature in the opening of said spacer block.
 18. The kit as claimed inclaim 16, wherein the alignment rail comprises an elongated projectionand the alignment feature comprises an elongated groove that receivesthe elongated projection.
 19. The kit as claimed in claim 17, whereinsaid posterior resection guide locator includes an alignment pin guideoverlying said alignment rail, wherein said alignment pin guide includesat least one pin opening extending therethrough.
 20. The kit as claimedin claim 19, wherein said bur template includes a guide rail extendingaround an outer perimeter thereof and a central opening surrounded bythe guide rail, and wherein said at least one pin opening of saidalignment pin guide is aligned with the central opening when saidalignment rail is inserted into the opening of said spacer block. 21.The kit as claimed in claim 20, further comprising an alignment pininsertible into the at least one pin opening of said alignment pinguide.
 22. The kit as claimed in claim 21, further comprising aposterior resection guide including an upper end, a lower end having anelongated opening for receiving a cutting tool and a pin opening betweenthe upper and lower ends, the pin opening of said posterior resectionguide being slidable over the alignment pin.
 23. The kit as claimed inclaim 19, wherein the pin opening includes a first set of pin openingsand a second set of pin openings that is closer to the upper end of saidposterior resection guide than the first set of pin openings.
 24. Thekit as claimed in claim 20, wherein the pin opening includes a third setof pin openings that is closer to the lower end of said posteriorresection guide than the first set of pin openings.